There is conventionally known an emergency report apparatus that, in the event of an emergency in a vehicle, establishes data communication with an emergency report center through a wide-area wireless communication network (e.g., a mobile phone communication network) in order to let an occupant of the vehicle converse with an operator at the emergency report center (refer to Patent Literature 1).
However, in the event of an emergency where the vehicle is damaged, loudspeakers in the vehicle may become defective. If the loudspeakers are defective, the occupant of the vehicle is unable to converse with the operator at the emergency report center. In order to avoid such a contingency, there is a well-known technology for providing the vehicle with a backup loudspeaker in addition to normally used main loudspeakers and using the backup loudspeaker to output a voice message from the operator at the emergency report center when the main loudspeakers are defective.
A well-known method of diagnosing a defect in a loudspeaker is to output a DTMF (Dual-Tone Multi-Frequency) sound or other diagnostic sound from the loudspeaker and detect the outputted diagnostic sound with a microphone.